As gold has seen its best start to the year since 1974, exchange-traded funds that track the metal have surged in popularity. According to Stacey Gilbert of Susquehanna, long unlevered gold ETFs have already seen $7.3 billion in inflows this year.

"It is definitely a fan favorite this year," Gilbert said Thursday on CNBC's "Power Lunch." "Just to put in perspective of when we've seen those flows in the past — two months into the year — it was 2009."

The most popular gold ETF, GLD, has grown by $5.5 billion this year, according to ETF.com data. That's more than twice the net inflows seen by the second-most popular ETF, iShares MSCI USA Minimum Volatility (USMV).

Demand for gold has been so strong that new shares of the iShares Gold Trust fund (IAU) were suspended temporarily from being issued in March. In February, IAU saw its largest creation activity in a decade.

Contributing to the recent run to safe-haven gold have been concerns over economic weakness and a global stock market rout. But even as U.S. stocks have rallied greatly off this year's lows, Max Wolff of Manhattan Venture Partners said the prospect of negative interest rates has also sent investors flocking to gold assets.

"They're running to wherever they can because zero looks better than a loss, and some of that money is being forced into gold," Wolff said Thursday in a "Trading Nation" segment. "I'd be very cautious about buying it here, but if it sells off a bit, I'd get back in."

Gilbert, Susquehanna's head of derivative strategy, said the options market is signaling more likelihood of a big move higher for gold than a big move lower, as options traders remain more bearish on the broader stock market.

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Trading Nation is a multimedia financial news program that shows investors and traders how to use the news of the day to their advantage. This is where experts from across the financial world – including macro strategists, technical analysts, stock-pickers, and traders who specialize in options, currencies, and fixed income – come together to find the best ways to capitalize on recent developments in the market. Trading Nation: Where headlines become opportunities.

Michael Santoli joined CNBC in October 2015 as a Senior Markets Commentator, based at the network's Global Headquarters in Englewood Cliffs, N.J. Santoli brings his extensive markets expertise to CNBC's Business Day programming, with a regular appearance on CNBC's “Closing Bell> (M-F, 3PM-5PM ET). In addition, he contributes to CNBCand CNBC PRO, writing regular articles and creating original digital videos.

Previously, Santoli was a Senior Columnist at Yahoo Finance, where he wrote analysis and commentary on the stock market, corporate news and the economy. He also appeared on Yahoo Finance video programs, where he offered insights on the most important business stories of the day, and was a regular contributor to CNBC and other networks.